Matt Berninger, the lead singer and songwriter for New York indie group the National insists he couldn’t sing or write when he joined his best friend’s rock band in college.

“I was lucky to be friends with guys who were amazing musicians,” he tells The Post from a tour stop in London. “I couldn’t really sing at all.”

But maybe he’s just being modest. After all, the National just released its third album, “Boxer,” and starts five straight sold-out shows, at the Bowery Ballroom tomorrow.

Berninger, 36, got great advice along the way, starting with that college pal – Scott Devendorf, one of his bandmates with the National.

To learn the ways behind a mike, Devendorf advised Berninger to listen to Guided by Voices’ Bob Pollard, who “just sings with his heart.”

Berninger couldn’t play guitar either, so he gravitated to writing lyrics, finding inspiration in the words of Morrissey, Nick Cave and Leonard Cohen.

“They made me realize rock ‘n’ roll is an important thing. It has depth. It’s not just entertainment.

“All songs need a certain amount of stupidity and sincerity,” he says. “You need to find the right balance.”

The quintet needed to find some balance, too, after the tour for their sophomore disc, “Alligator.”

“We felt worn out and beaten down,” Berninger says. “It took a long time to make the new album.”

The album’s title “Boxer” refers to how the band felt as well as to some of the songs’ characters.

“There’s the idea of people being on the ropes or struggling to hold onto things,” he says.

The Brooklyn-based band was so wiped out after that tour, the members disappeared for a few months to recover themselves.

“We needed to re-energize and live normal lives for a little while, so we had stuff to write about,” says Berninger. “We didn’t want to write songs about driving around in a van. We needed to water our roots,” he says.

Those roots are actually in Cincinnati, but the fivesome, which includes Berninger and two sets of brothers – Scott and Bryan Devendorf and Aaron and Bryce Dessnor – didn’t form the National until the late ’90s, after everyone had moved to Brooklyn.

The new disc features the Clogs’ Padma Newsome, who adds orchestral touches to its rootsy, Britpop, post-punk blend, and Aaron’s indie-rocker neighbor Sufjan Stevens.

Even after its completion, Berninger is still working on stabilizing the relationship between rock and a normal life.

“We’ve always written things about being home and simple problems and relationships and day jobs. For us, it was always an escape from our day job. Now it’s turning into a real job. It’s a strange shift.”